Because you answered it incorrectly; 42 is the Ultimate Answer to the Ultimate Question of Life, the Universe, and Everything. Neither the answer nor the question have any meaning unless you put them together, but if you were to put them together, it is thought that the universe as we know it would cease to exist and be replaced by an infinitely more complex universe.
Have you read all five novels of Douglas Adams' Hitchhiker's Guide to the Galaxy trilogy?